were assembled inside pressure cooker pots similar to this one packed with bbs, ball bearings and nails to magnify the injury. as these homeland security bulletins note, pressure cookers have been used for decades in terror bombings. instructions for making them appear on the internet including just last month in an al qaeda magazine "inspire." investigators say the explosive in boston was most likely smokeless powder, gunpowder like this, available at sporting goods stores, not something more powerful like dynamite. and they believe the bombs were carried to the scene in dark nylon bags and set off by timers. the fbi is examining photos like this from nbc affiliate whdh to see if nylon bags might have been placed in trash bags on the sidewalk to appear less conspicuous. a former bomb investigator says the experts know what to look for. >> they are able to recognize the minute pieces of an article that a civilian wouldn't even know what it was, but a bomb investigator like fbi or atf

will say, that's from a clock. that's from a battery. >> reporter: boston police say the area was checked twice for bombs yesterday, but there was no security screening. >> because there is unrestricted access to the race course, simply because it's 28 miles long, people can come and go and bring items in and out. >> reporter: authorities last night searched the apartment of a foreign student who was injured in the blast and seen running away, but they found nothing, and he is not considered a suspect. investigators urge anyone who was at the scene yesterday to send them pictures and videos. one person responding, ben thorndike, who works in a building that overlooks the finish line. he snapped these pictures in rapid sequence immediately after the first explosion. one person can be seen running away, clothes torn by the blast. >> i just kept the camera up, just pushed the rapid shutter button down and just took, you know, 25 pictures over the course of -- if felt like a long time, but i think it was only 15 or 20 seconds. >> reporter: police and federal

agents even took the highly unusual step of asking people leaving boston at the airport today if they had pictures of value, too. and this breaking news on another note. an unrelated note. the fbi is analyzing an envelope sent to a u.s. senator but intercepted at an off-site mail site. a field test indicated it was positive for the poison called ricin. it's now in the lab to see if it really is that chemical. brian? >> reporter: pete williams in our washington bureau tonight. pete, thanks. and after this sad, depressing day in boston, lester holt, part of our team here, is here tonight with the news of this day. lester? >> brian, this heavy police presence will be a way of life for boston residents for some time to come, but there were thousands of visitors here, spectators, they came to bear witness to a great sporting event. instead they are filing out of town having beared witness to terror. >> reporter: a runner, a camera strapped to her body with a view of the finish line on the horizon. a view that changes in an

instant. it is one of countless images that captured the day, images authorities hope also captured the bombers. >> something just blew up. >> there has to be hundreds, if not thousands, of photographs or videos or observations that were made down at that finish line yesterday. and they're sitting out there amongst everyone that's watching this event this morning. >> i need officers. a secondary device! >> reporter: recordings of emergency radio traffic have been released. >> there's multiple people down! >> reporter: illustrating the urgency of yesterday's response. and today another of the dead was identified. 29-year-old krystle campbell of medford, massachusetts. >> everybody that knew her loved her. she loved her job. she had a heart of gold. she would always smile. you couldn't ask for a better daughter. i can't believe this has happened. >> reporter: allen panzer, a

north carolina emergency room physician, was waiting for his wife to cross the finish line. he saw the explosion and attended to the most seriously wounded. >> it was blast injuries to the lower extremities for the most part. one gentleman had no legs below the knees. >> reporter: investigators say the bombs were placed among the crowd down the block from each other, detonating just over ten seconds apart. officially, it was back to business in most of boston today. but reminders are everywhere that things are not back to normal. >> you see people, and their faces are really sober, just walking around. it's kind of an eerie feeling in the air. >> reporter: today runners were able to return to the route to collect belongings that were left in the haste of yesterday's flee to safety. some were given medals for a race they were unable to complete. medals hopelessly tarnished by tragedy. >> i ran 22 miles thinking about the minute when i was going to come down the street and get this medal. and it's, like, this is not how

i wanted it, but it's around my neck, and i was a part of this day. >> reporter: there are any number of stories that will break your heart here including the story of the second victim, krystle campbell. her parents were first told that it was her friend who died, brian, but doctors had to return and tell them it was krystle who passed away. >> lester holt here with us in boston, thanks. you hear the church bells behind us. they started off with "god bless america" a few minutes back. this entire city, of course, consumed with what happened yesterday. and so many questions and stories about the victims of this. katy tur, part of our team here as well, she's been looking into the victims all day. good evening. >> brian, they were standing on the sidelines cheering on loved ones, friends and even strangers. then all of a sudden chaos. tonight we're learning more about the trauma of those first few moments including the victims. and an 8-year-old boy excited to see a marathon. >> reporter: today neighbors remembered 8-year-old martin richard, the youngest of the victims.

>> to know that that little boy will never come home again is -- it kept me up tonight, and it will probably keep me up more nights. >> reporter: martin was in the crowd watching the marathon with his parents, 11-year-old brother and 5-year-old sister close to where the blast went off. he was killed. his mom and sister right now are in very bad shape. in a statement, his father, bill richard, wrote, "my dear son martin has died from injuries sustained in the attack on boston. my wife and daughter are both recovering from serious injuries. we thank our family and friends, those we know and those we have never met, for their thoughts and prayers." >> we're a very close community, and we are all devastated. >> reporter: the drawing he made in front of his home over the weekend drew neighbors and friends who left flowers and candles in remembrance of the young boy. at the finish line it only took moments for a joyous accomplishment to turn to terrifying confusion. 78-year-old bill iffrig was just feet from the explosion, about

to finish his 45th marathon. what did it sound like? what did it feel like? >> it was so loud. boom! >> reporter: what have your kids said to you? >> they said, dad, you are so lucky. yeah, i was really lucky that it ended up like it did. >> reporter: the families of newtown shooting victims were at the race, but none were injured. still many others were. >> it was an extraordinary horrible scene, and what we were able to do is pull together what we needed to pull together in a very short period of time. >> just didn't seem real. >> reporter: leeann and nicholas were watching the race. she was left with shrapnel in her leg and a shattered femur. now she remembers the compassion of those who rushed to help. >> i had a woman who i don't know came and held my hand. >> reporter: 30 code red victims with life-threatening injuries taken to hospitals. they and dozens of others are trying to recover tonight.

and right now 24 remain in critical condition. regional blood banks are asking for donations from surrounding states, brian, as boston has depleted all of their supplies. >> as we said, it's consumed this entire city. katy tur here with us in boston. thanks. and tonight, governor of massachusetts deval patrick is with us from the command post at the westin hotel not far from us here. governor, thank you for being with us. first of all, is there anything you've been on the inside all day, anything you've learned? any imagery you've seen that would lead us to believe they're any further down the road? >> well, i think your reports about the status of the investigation are pretty thorough. what we know, we have made public or most of it anyhow. the investigators at the federal, state and local level are coordinating beautifully, and we have every conceivable asset on the ground, and they are literally combing the blast site with a fine-tooth comb to piece together what happened and

ultimately the story of how and bring whomever is responsible to justice. it's a slow process. it's a painful one. but there are also alongside this, brian, some extraordinary stories of grace and kindness that people have shown, both neighbors from massachusetts and visitors from outside of the city and the state. >> i heard your public plea, governor, a young woman who was helped by an army sergeant just back from afghanistan. you're helping to find him to reunite him with her. one final question before we lose you. and that is, it was striking yesterday, this happened with boston pd officers in the foreground, meaning if you can get a device into an already secured area, what's that going to mean for defending cities like boston? >> well, i think the thing to remember here -- maybe two things to remember. first of all, the first job of

everybody is to figure out who is responsible for what happened and precisely what happened and to bring that person or persons to justice. and that's what law enforcement is focused on. the second thing, then, is to sort out how this could have happened. you know, we've had 116 years of incident-free marathons. and every year we have learned lessons from the one before. it's a terrible, terrible and bloody lesson we're having to learn this time. but i am also confident that we will learn what lessons there are to be learned, and next year's marathon will be bigger and better than ever. >> the governor of the commonwealth of massachusetts, deval patrick, thank you very much for being with us. we'll be back with more news from boston and elsewhere right after this.

we're back at the corner of the public garden here in boston. the next major marathon is this sunday in london. for that matter there's a major sporting event every day all

year all around the world. and this raises questions about how to defend and secure those. tom costello is at the verizon center in washington where there's an nhl game tonight. the capitals playing the toronto maple leafs. tom, good evening. >> reporter: hi, brian. and the attack on boston very much on the minds of people here as well as at sporting events across the country. but there is also a determination not to bow to terrorists. on this day after, many americans felt on edge like they haven't in years. suspicious packages brought boston's logan and new york's laguardia airports to a crawl today. both were later deemed safe. in washington, a heavy police presence in the subways. pedestrian traffic in front of the white house shut down. capitol police checked every trash can for explosives. while at the emancipation day parade, both unease -- >> i was kind of concerned as to who's here, you know, why they're here, if anything's

going to happen. are we safe? >> reporter: -- and defiance. >> i came down. i'm not going to be afraid. this is my home. >> reporter: across the country, police departments were showing the badge today. the tsa also stuffing up passenger screenings. meanwhile, event organizers began revisiting security plans for big upcoming gatherings. the oklahoma city marathon, a bike race in houston, a 10k in miami, nascar in virginia, even the kentucky derby and indy 500 getting a second look. >> i think the event in boston yesterday will raise once again the consciousness that there is a reason, there is a need for the extra security that they encounter. >> reporter: since 9/11, there's been a dramatic increase in the use of security cameras. today an influential republican called for even more. >> out on the street, there's not an expectation of privacy. >> reporter: at the lapd intelligence nerve center, the police chief insisted his cameras and officers can't do it alone. >> there is no way that 10,000

los angeles police officers can watch over a city of 4 million people. without the help of the people that they're watching. >> reporter: the message since 9/11, if you see something, say something. police and security experts are reiterated to us today that they really want people to call in with tips and with even the smallest bits of information. they point out that in the past, those small clues have very often been the key to tracking down a criminal or breaking a terror suspect or cell. brian? >> tom costello at the caps/maple leafs game, thanks. there was other news today. we'll be back with that right after this.

a huge story, a computer problem took down the american airlines reservations and check in system. for a time, the entire airline grounded its fleet.

they said it was a glitch and not a hack. american terminals around the country were jammed with delayed passengers and arriving aircraft. landing unannounced in many cases at airports across the country. they were forced to sit on tarmacs with no gates available to offload passengers. more than 700 flights were canceled. nearly 1,000 delayed before things got straightened out. but a very bad day at american airlines. this next story would have received broad coverage were it not for this terrorist bombing in boston. a bipartisan review board has found it indisputable in their words that the united states has engaged in the practice of torture since 9/11. they say the highest officials in our country bear responsibility and share responsibility for it. the report says torture has damaged the standing of our nation. on top of potentially increasing the danger to u.s. military personnel taken captive, on top of all of it, the commission found no evidence that torture ever yielded any key information. no information that we are any safer because of it.

and we learned late today, pat summerall has died. he was a veteran kicker in the nfl but most of us came to know him as the voice of the nfl. first with his partner, tom brookshire and for years with the great john madden. he called 16 super bowls. he was in the booth for four decades. after a life spent on the road, he went public about his own alcoholism. years ago he underwent successful rehab. he helped set the modern day standard for may by play as an art form. he died in dallas, texas, at the age of 82. we're back in a moment with some of the stories that emerged today here in boston. those who stepped up at an awful moment yesterday.

finally tonight from boston, inevitably when something bad like this happens, terrific stories of heroism and kindness emerge. nbc's anne thompson whose roots are here has the story of this city today. >> reporter: if crisis reveals character, then call boston courageous. carlos arredondo, the man in the cowboy hat, is one of many who

ran to help instead of running away. >> i was carrying someone who lost both of their legs. >> reporter: in the midst of the horror, he remembered his lowest point, when he learned his son alex, a marine, had been killed in iraq. grief stricken, he set himself on fire and was rescued. he recalled his wife's words of comfort as he calmed jeff baumann jr. baumann lost his lower legs but survived. >> what i experienced myself, i give something to comfort him and give him hope and get him out of there as soon as we could. >> reporter: you can call boston kind. peter deandrade lives two blocks from where the bombs went off. leftovers from his pre-race party were post-race sustenance to confused runners. >> we carried everything out on platters and started feeding people and brought out coffee. the little things we could do, my friends and i, to help people out in this tragedy. >> reporter: boston at times has been divided by class, ethnicity

and race, but it's always come together on marathon day, never more than in 2013 when nearly 6,000 people offered their homes online to stranded runners. yes, you can call boston generous. marguerite smith invited three runners and their five friends into her home and fed the shivering group from kansas city. >> they were sitting there not able to get into their hotel, not having eaten, and they weren't complaining. they were just very charming. >> reporter: one of the runners, allie hatfield, posted pictures on her blog writing "people are good." and tonight you can say that about boston, too. anne thompson, nbc news, boston. and one more note before we go. it takes something big for this to happen. the yankees and red sox logos side by side right there on the side of yankee stadium in the bronx where tonight the yankees will pause to play the fenway anthem "sweet caroline" as the ultimate show of support for boston. the rivalry takes a break.

it will be back. that is our broadcast for this tuesday night from boston. thank you for being here with us. i'm brian williams. we'll look for you back in new york tomorrow night. good night. ♪ it shows that the culture that the issue of safety is something that has not been a priority. >> we investigated, now a state lawmaker is demanding action from the governor. right now at 6:00, the shakeup he's calling for at the california public utilities

commission. plus a highly anticipated hearing for the south bay teens accused of sexually assaulting 15-year-old audrie pott. >> frantic moments for a father and son who were at the finish line at the boston marathon when the bomb went off. good tuesday evening. i'm janelle wang. raj mathai is on assignment. >> i'm jessica aguirre. tonight more bay area families are sharing their stories of terror in boston. what was supposed to be the memory of a lifetime, crossing that finish line at the historic boston marathon, turned into pure panic and confusion. terry mcsweeney joins us from boston where he spoke to a father and a son from los altos. they were just looking to have that ultimate running experience, but really they had the ultimate bonding experience. >> reporter: that's true. yesterday was going to be a very

memorable day for the anderson family of los altos. father and son running together in the boston marathon. obviously it's a memorable day, but not for the reason they had hoped. here in boston tonight memorials like this going up here and there. this one on the street where the bombs went off. people stopping by to offer their prayers and thoughts for the victims. the andersons, meanwhile, are offering thanks for each other. >> this was going to be, you know, our moment. >> reporter: and in a tragic way, it was the moment for bob anderson of los altos and his son, michael. they came to boston to run the marathon. bob finished before michael and was waiting for his son just past the finish line, just before 2:00. >> you could hear the sound of the bomb and the smoke. oh, my god. at that moment, i mean i didn't know where my son was. moments later there was a second

bombing or explosion and it was just -- it was just unbelievable. >> reporter: police were herding people away. bob says he didn't panic, but he knew his son hoped to run about a four-hour marathon, and the bombs went out shortly after that mark. the emergency meeting place for the andersons was the hotel. and after what seemed like days, michael turned up there. >> mike came in and we both just hugged each other. i just said, mike, i love you so much. are you okay? and that was it. i mean we just -- we hugged each other. but it's -- it's just unbelievable. >> reporter: what you're looking at out here on the street where the bombs went off is one of the medals given to those who finish the boston marathon. someone offering it up in